[media] s5k6aa: Use devm_regulator_bulk_get API

devm_regulator_bulk_get is device managed and saves some cleanup
and exit code.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>